The invention relates to a cutting assembly for cutting thread, and is particularly adapted for use with automatic sewing machines for cutting synthetic stitching thread after sewing with such machines. Conventional hot wire cutters in the textile industry, particularly those utilized with automatic sewing machines, have a number of drawbacks associated therewith, which the present invention is designed to overcome.
Conventional automatic hot wire cutters utilize a vacuum source to effect removal of severed stitching thread, and cause the thread to move over the hot cutting wire. The hot wires in such cutters typically do not operate ideally, however, since they either operate too cooly, so they do not effect the cutting action properly, or if the current therethrough is increased substantially they burn up too quickly. It has been found -- according to the present invention -- that the location of the hot wire directly in the primary stream of air flowing into the vacuum conduit results in this less-than-ideal operation.
Also, conventional cutters are either manual or automatic, and this limits their versatility and utilization for some operations. For those operations where an automatic action will be required at sometimes, but manual passage of thread into contact with the hot wire during related functions is desirable, the prior art has failed to provide a satisfactory alternative.
Further, conventional hot wire cutting assemblies utilizing a vacuum source provide the vacuum source at a location remote from the cutting action, and the vacuum-providing structures normally are relatively cumbersome and difficult to deal with.
According to the present invention a cutting assembly for cutting thread, and particularly adapted for utilization in textile operations with automatic sewing machines for cutting synthetic stitching thread, is provided that overcomes the limitations and drawbacks inherent in the prior art.
According to one aspect of the present invention, the cutting assembly is provided including a guide block having a bottom surface for movement of cloth therepast in a direction A, with a means defining a narrow channel in the guide block substantially parallel to the direction A, the channel being open at the bottom surface and having a trailing end and a leading end spaced from each other in the direction A. Means are provided defining a vacuum cut-thread removal passageway in the block at the channel leading end, and in operative communication with the channel, the passageway being elongated in the dimension intersecting the channel. A first wire portion of electrically conductive material is adapted to be connected to a source of e.m.f., and means are provided for mounting the wire portion in the channel spaced from the channel bottom so that the wire extends into the channel generally perpendicular to the direction A adjacent, but spaced from, the intersection of the channel and the vacuum passageway, out of the primary flow of air into the vacuum passageway. By mounting the wire portion out of the primary flow of air, it does not have a tendency to cool as rapidly as if mounted in the primary flow of air, and thus the energy supply thereto can be minimized while effective cutting action is provided.
According to another aspect of the present invention, the cutting assembly provides a dual-exposure of the cutting wire, allowing both automatic and manual cutting to be performed therewith. Means are provided defining a notch in the block adjacent, but spaced from, the channel leading end, the notch including an open bottom and end.
The means for mounting the wire mount it so that it also extends into the notch so that thread may be moved into the notch through the bottom and/or end into contact with the wire to be severed thereby. Mounting of the wire can be accomplished in a simple manner which allows adjustability of the spacing of the wire from the channel bottom, to thereby vary the length of the stitching thread being cut that remains with the cloth (i.e. the remaining nub). The block may be of metal, and a ground screw may attach one end of the wire to the block, the block being connected to ground. In that way only one wire need lead to the block.
Vacuum withdrawal of cut thread is provided in a simple and effective manner. A relatively short vacuum conduit is in operative communication with the vacuum passageway, and is connected to a first, through-passageway in a small integral component block mounted close to the guide block. A second passageway is formed in the block, intersecting the first passageway, and a third, blind passageway is provided in the block having a fitting at the end thereof adapted to be connected to a source of air under pressure. The intersection between the second and first passageways is such that air flowing through the third passageway, and second passageway, into the first passageway, moves away from the guide block, thereby providing a vacuum in the vacuum conduit and vacuum passageway. A conduit extending from the integral block first passageway, opposite the vacuum conduit, eventually deposits the withdrawn thread into a waste receptacle.
It is the primary object of the present invention to provide a simple, effective, and versatile cutting assembly for cutting thread. This and other objects of the invention will become clear from an inspection of the detailed description of the invention and from the appended claims.